Transition metal bis-diazabutadienes [(DABD)2M] have been previously identified as precursors that enable the selective ALD or CVD of transition metals on metallic surfaces. See, C. Winter et al, Organometallics 2011, 30, 5010-5017. In addition, (DABD)2M precursors avoid deposition on adjacent dielectric surfaces such as SiO2 or low dielectric constant organic interlayer dielectrics (low-k ILDs). This selectivity is a characteristic of the chemical make-up of the (DABD)2M precursors and chemical passivation of the undesired surface may not be required. However, existing methods of preparation of M-DABD are relatively low yielding and plagued by the formation of undesired by-products (Winter et al).
The growth of material layers by ALD generally involves the following steps: (1) exposure of the substrate to a first precursor of an organometallic compound that modifies the substrate surface; (2) purge or evacuation of the reaction chamber to remove non-reacted precursors and other gaseous reaction by-products; (3) exposure to a second gaseous chemical composition that reacts with the modified substrate surface to form a film. A purging gas may then be introduced to remove any residual second chemical composition and the steps may be repeated.